The root cause of the fire that sparked a major power outage at Heathrow Airport remains unknown, the UK’s national energy system operator has said.

The blaze in March at the North Hyde Substation, which supplies electricity to Heathrow about 1.5 miles away, caused a power outage, which meant Europe’s biggest airport had “no choice but to close” for 16 hours.

More than 1,000 flights to and from Heathrow were cancelled, and more than 270,000 air passenger journeys were disrupted.

Tens of millions of pounds were lost, thousands of passengers stranded and questions raised about the resilience of the UK’s infrastructure.

The National Energy System Operator (NESO), in its interim findings into the North Hyde Substation outage, said forensic investigations were ongoing.

The Metropolitan Police previously confirmed on 25 March that officers had “found no evidence to suggest that the incident was suspicious in nature”.

The interim report stated that one of North Hyde substation’s three supergrid transformers – devices which enable voltages to be stepped up or down so electricity can be efficiently distributed – became disconnected, known as tripping, at 11.21pm on 20 March.

It was later confirmed to have caught fire.

At 11.49pm, the adjacent transformer also tripped, which resulted in the simultaneous loss of connection to the remaining transformer, according to the document.

NESO anticipates that the final report, due to be published in June, is expected to make findings and recommendations relating to the resilience of energy infrastructure in the UK, the response and restoration of energy infrastructure, and the resilience of critical national infrastructure to energy disruption.

Power was restored to the terminals around seven hours before flights resumed, investigators said, noting the flow of electricity to all four passenger terminals was restarted by 10.56am on 21 March.

The airport was shut for most of that day, before flights resumed around 6pm.

NESO said power was restored to the “wider Heathrow Airport Limited network” by 2.23pm.

That was followed by “a period of safety checking” to ensure “safety critical systems were fully operational prior to passengers arriving at the airport”.

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Heathrow Airport said in a statement it welcomed the review which raises “important questions” for National Grid – which owns the substation that caught fire – and Scottish and Southern Electricity Networks (SSEN), which is responsible for power distribution in the area.

A spokesperson said understanding more about how the fire started and “why two transformers were subsequently impacted can help ensure greater resilience for the UK’s energy grid moving forward”.

Energy Secretary Ed Miliband also welcomed the NESO report, admitting the fire and power loss led to “major disruption to thousands of people and many businesses”.

He said the initial report into the incident “rules out the possibility of any suspicious activity.

“We now await the full report to understand what happened and learn lessons to strengthen UK energy resilience and protect our critical national infrastructure.”

Heathrow is the world’s fourth-busiest airport, handling 84.1 million passengers from March 2024 to February 2025.

A 101-year-old veteran, who has never publicly talked about her wartime experience, wants the VE Day 80th anniversary events to be a chance to reflect on the “unnecessary” conflicts we see today that she says are driven by “pure greed”.

Pauline Alexander was one of five siblings who all served in the Second World War – with three of them among the four family members she lost during the conflict.

She was encouraged to talk about what she went through by her daughter after she saw the Royal British Legion appealing for more surviving veterans to tell their stories.

80 years ago, as Sir Winston Churchill declared there was finally victory in Europe and the celebrations erupted in London, Ms Alexander was in Chelmsford with her mother and sister-in-law.

“I was at home on leave,” she said.

“We joined in the celebrations, the singing and dancing. It was very exciting. Everyone in Chelmsford had turned out, well those who were still there. But it was very… how can I put it? A feeling of what next… life had changed completely.

“We started [the war] as a family of seven, we ended as three.”

Like so many, Ms Alexander’s war was punctuated by loss.

Her father died while running the family surgical instrument business in 1943, and three of her brothers were killed.

Peter Kipling, an Army dispatch rider, died in a bike accident delivering a message to the war office in London. He was about to be sent to the front in preparation for D-Day.

Guy and Bernard Kipling, who were twins, were both navigators on RAF bombers.

They were shot down in 1941 and 1943, their bodies never came home.

All three are remembered on Peter’s gravestone in Broomfield Cemetery.

Looking at photographs of her brothers, Ms Alexander quietly said: “That’s just how I remember them all, just like that.”

When I asked her how she felt when she heard they had died serving their country, she replied: “In those days of war you just had to accept these things.

“It was bound to happen at some time or other. Bernard served on Whitley bombers, and they were known as flying coffins.”

Ms Alexander’s story about her family, and the clerical work she did in the Women’s Royal Air Force (WRAF) from 1942-1946, including at bomber command at RAF Waddington, only came to light because of the Royal British Legion appeal.

She said she previously just thought: “It was our duty to do what we could and that was life, everyone was losing family… it was just something that happened.

“All part of life and living.”

I asked her how her mother reacted when she said she wanted to sign up.

Ms Alexander replied: “She said yes. It would do me good. I was getting too spoilt at home.”

She added: “If my brothers were in, I had to be in to do my bit too.”

Her mother, Rosa Kipling, was also a remarkable woman.

She lived until 105 and was recognised for bravery in the first honours list to feature MBEs in 1918, after surviving an explosion during the First World War in a munitions factory.

It is no wonder then that her children were all so committed to do their bit.

The sense of service and the acceptance of the sacrifices that had to be made now feel more important than ever, especially in the context of ongoing global conflicts.

That was something that Ms Alexander was keen to talk about from her home in March, Cambridgeshire, where she will be watching today’s events.

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Asked why she believes it is so important that we take time to remember today, she said: “Because it’s all part of history, and history is very important, because we learn from history.

“When you think of all the conflicts that are going on now and how it’s all unnecessary in a sense, just pure greed. Because what they went through [in the Second World War] was absolute hell.”

As I reflected with her that they truly are an amazing generation, Ms Alexander simply replied: “Yes, there’ll never be another one like it.”

A man has appeared in court, charged with murder after a stabbing inside a bank in Derby city centre.

Haybe Nur Cabdiraxmaan, 47, from nearby Normanton, was remanded in custody at Southern Derbyshire Magistrates’ Court on Thursday.

Gurvinder Singh Johal, 37, died after he was stabbed inside a Lloyds bank on Tuesday, the Crown Prosecution Service said.

He was pronounced dead at the scene after the emergency services were called at around 2.35pm.

Nur spoke through a Somali interpreter, who attended the hearing via video-link.

During his eight-minute appearance, he confirmed his name and date of birth and told the judge: “I don’t know where I live – somewhere there.”

The defendant, who was arrested at an address in Western Road, appeared in the dock dressed in grey jogging bottoms and a round-necked sweatshirt.

A second man, in his 30s, who was arrested in connection with the incident, has been released with no further action, Derbyshire Constabulary said.

Adjourning the case, District Judge Stephen Flint told Nur: “I must send your case to Derby Crown Court. Tomorrow a Crown Court judge will decide what happens next in this case.”

The judge also offered his condolences to the family and loved ones of Mr Johal.

Samanatha Shallow, deputy chief crown prosecutor in the East Midlands, said: “Mr Johal died after a stabbing inside Lloyd’s bank in St Peter’s Street, Derby, after 2.30pm on Tuesday 6 May.

“Our thoughts remain with the family of Mr Johal at this time.”

Ms Shallow has warned the public against speculating about the incident online.

The hearing was watched by around 15 family members of Mr Johal, who was said to have been known to friends as Danny.

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In a tribute given to the Derby Telegraph on Wednesday, councillor Ajit Atwal, leader of the Lib Dem group on Derby City Council, who knew Mr Johal, called him “humble, quiet” and “kind”. He said he was someone who “would always go above and beyond for everyone.

“His family are devastated and cannot understand what has happened.”